(1) Field of the Invention
The present invention generally relates to an optical recording medium, such as an optical disk and a magneto-optic disk, and a data reproducing apparatus for reproducing data from the optical recording medium, and more particularly to an optical recording medium in which data is recorded at a high density and a data reproducing apparatus for reproducing data recorded in the optical recording medium at the high density.
(2) Description of the Related Art
In a field of an optical recording medium, such as an optical disk, from which data is reproduced using a light beam (a laser beam), it is desired that the data is recorded at a high density, and a 3.5-inch optical disk having, for example, a recording capacity of 128 MB has been proposed. In this type of the optical disk, for example, pits are arranged on lands which are recording areas so that the arrangement pattern of the pits corresponds to the arrangement pattern of "0" and "1" in recording data. It is detected, by scanning of the light beam, whether or not there is a pit on each land, corresponding data is reproduced based on the detection results.
As has been described above, in the conventional optical recording medium, since it is detected, by scanning of the light beam, whether or not there is a mark, such as the pit, having a optical singularity, the limitation of the data recording density depends on the wave length of the light beam (the spot size of the light beam). Thus, to increase the data recording density in the optical recording medium, a light source (a laser) which can be emit the light beam having a shorter wave length must be developed.